Senior Fullstack Developer - Freelancer (Ruby on Rails and TypeScript)

🏢 Summary: Freelance Principal Software Developer role focused on leading architecture and development of internal tools and admin panels using Ruby on Rails and React. The position requires strong end-to-end ownership, technical direction, and responsibility for system quality and evolution. You will design robust solutions, maintain comprehensive test suites, and collaborate closely with internal stakeholders. 🗂️ Requirements: 8+ years of software development experience, Senior-level expertise in Ruby on Rails, Senior-level expertise in React, Experience defining architecture and making technical decisions, Experience designing and maintaining robust test suites, Experience building admin panels and internal tools, Ability to translate stakeholder needs into technical solutions, Experience working in small-scale or internal environments, Ability to work independently and take technical ownership 📃 Skills: Ruby, Rails, React, JavaScript, Testing, Architecture 🏢 Description: We’re specifically looking for a Principal Software Developer (Ruby on Rails & React) - Freelancer What We’re Looking For A Full-Stack Craftsman: You are an expert in Ruby on Rails and TypeScript , capable of building everything from complex dashboards and billing UIs to sleek documentation platforms. The "DevEx" Champion: You have a natural empathy for other developers. You’ll develop deep knowledge of our platform (Pub/Sub, Chat, LiveSync) and use the product yourself to gain a first-hand understanding of the developer experience. Comfortable with Ambiguity: You thrive in high-level vagueness. You can take a feature from a loose concept to a shipped product with minimal hand-holding, identifying problems and proposing solutions independently rather than waiting for a roadmap. Accountable & Reliable: You take pride in high-quality, well-tested code. You meet your delivery commitments, provide realistic estimates based on technical complexity, and communicate proactively if a timeline is ever at risk. An Owner: You monitor what you build in production and take personal ownership of quality issues. You see a feature through its entire lifecycle, from the first line of code to the final metric. What do we mean by freelance? Read more at Monterail Tech Network

🏢 Summary: Senior/Lead Ruby on Rails role focused on leading backend architecture and development while supporting frontend integration with React. The position involves driving technical direction, ensuring scalability and performance, and maintaining high code quality across the project. The role also acts as a technical point of contact aligning engineering outcomes with business goals. 🗂️ Requirements: Mastery of Ruby on Rails, Expert-level Ruby proficiency, Experience designing scalable backend architectures, Experience with React, Proven experience leading technical projects or modules, Ability to conduct code reviews and enforce best practices 📃 Skills: Ruby, Rails, React, Backend, Architecture, REST, Git, SQL 🏢 Description: We are looking for a high-level Ruby on Rails Expert to take a key role in the development team. This position is designed for someone who excels in backend architecture but can also navigate the frontend landscape when needed. As a Senior or Lead Developer, you will be responsible for the technical direction of the project, ensuring high performance, and maintaining a robust codebase while communicating effectively with international stakeholders. Responsibilities Technical Leadership: Leading the backend development lifecycle using Ruby on Rails . Architecture: Designing and implementing scalable, secure, and maintainable backend services. Full-stack Support: Collaborating on the frontend layer, specifically with React (experience here is a big plus). Code Quality: Conducting code reviews, mentoring team members, and establishing best development practices. Communication: Acting as a technical point of contact, ensuring clear alignment between technical goals and business needs. Requirements Expertise: Mastery of Ruby on Rails and the Ruby language. Frontend: Practical experience with React (highly desirable). Ownership: Proven ability to lead projects or significant technical modules. Soft Skills: Proactive attitude, strong problem-solving skills, and a "Lead" mindset.

🏢 Summary: Senior individual contributor engineering role focused on building and delivering scalable software, driving technical direction, solving complex problems, and mentoring engineers while remaining hands-on with development. The position involves working across backend and frontend systems using Ruby, Rails, React, PostgreSQL, Redis, Kafka, Elasticsearch, and Kubernetes. 🗂️ Requirements: Strong experience with Ruby, Experience leading complex cross-team projects, Ability to solve complex technical problems, Ability to work independently in ambiguous environments, Strong communication with technical and non-technical stakeholders, Experience mentoring engineers 📃 Skills: Ruby, Rails, PostgreSQL, Redis, React, Kafka, Elasticsearch, Kubernetes 🏢 Description: We are looking for a Senior Engineer to join our team and help us build and deliver software at scale. We have a flat structure, but this is a very senior individual role for someone who can make a big impact. In this role, you will take initiative, solve complex problems, improve our technical standards, and support other engineers. You will work closely with leadership to shape our technical direction while still writing code. Our Tech Stack Ruby 3.3.8 & Rails 7.2 PostgreSQL & Redis React (frontend) Kafka, Elasticsearch, Kubernetes (K8s) What you will do Drive technical work: Help turn high-level goals into clear projects and plans. Support the team: Mentor both junior and senior engineers to help them grow. Set standards: Improve how we work and make sure our code stays maintainable in the future. Handle uncertainty: Work without clear instructions at times, set direction, and guide others. Solve complex problems: Take the lead on difficult issues and important technical decisions. What we are looking for Strong experience with Ruby Experience in HR, Fintech, or Accounting systems is a plus Proven impact: experience leading complex projects across teams Good communication: able to work with both engineers and non-technical stakeholders Initiative: able to find important problems and follow through with solutions The process Screening call: 15-minute chat with a recruiter System design interview: 60-minute discussion about architecture Behavioral interview: 60-minute conversation about your experience and teamwork Final call: conversation with the CEO

🏢 Summary: Senior individual contributor role focused on building and delivering scalable software systems while shaping technical direction and standards. The position combines hands-on Ruby/Rails development with system design, cross-team technical leadership, and mentoring. The engineer will lead complex initiatives and drive architectural decisions in a modern distributed stack. 🗂️ Requirements: Strong experience with Ruby, Experience with Rails framework, Experience designing scalable systems, Proven experience leading complex cross-team technical projects, Ability to make architectural decisions, Experience mentoring engineers, Experience with distributed systems and backend integrations, Ability to work with PostgreSQL and Redis, Experience working with React frontend, Experience with Kafka, Elasticsearch, and Kubernetes 📃 Skills: Ruby, Rails, PostgreSQL, Redis, React, Kafka, Elasticsearch, Kubernetes, HR, Fintech, Accounting 🏢 Description: We are looking for a Senior Engineer to join our team and help us build and deliver software at scale. We have a flat structure, but this is a very senior individual role for someone who can make a big impact. In this role, you will take initiative, solve complex problems, improve our technical standards, and support other engineers. You will work closely with leadership to shape our technical direction while still writing code. Our Tech Stack Ruby 3.3.8 & Rails 7.2 PostgreSQL & Redis React (frontend) Kafka, Elasticsearch, Kubernetes (K8s) What you will do Drive technical work: Help turn high-level goals into clear projects and plans. Support the team: Mentor both junior and senior engineers to help them grow. Set standards: Improve how we work and make sure our code stays maintainable in the future. Handle uncertainty: Work without clear instructions at times, set direction, and guide others. Solve complex problems: Take the lead on difficult issues and important technical decisions. What we are looking for Strong experience with Ruby Experience in HR, Fintech, or Accounting systems is a plus Proven impact: experience leading complex projects across teams Good communication: able to work with both engineers and non-technical stakeholders Initiative: able to find important problems and follow through with solutions The process Screening call: 15-minute chat with a recruiter System design interview: 60-minute discussion about architecture Behavioral interview: 60-minute conversation about your experience and teamwork Final call: conversation with the CEO

🏢 Summary: The offer is for a Ruby on Rails Developer to build and maintain modern web applications for a new project, contributing to scalable solutions and microservices architecture. The role involves working with Ruby on Rails as the core technology, with exposure to Node.js and React, in a collaborative and agile environment. 🗂️ Requirements: Proven commercial experience with Ruby on Rails, Experience building modern web applications, Experience with Node.js and/or React, Understanding of microservices architecture, Ability to participate in code reviews and follow coding standards, Very good English skills 📃 Skills: Ruby, Rails, Node.js, React, Microservices, REST, Git 🏢 Description: We are seeking a skilled Ruby on Rails Developer to join our team for an exciting new project. Responsibilities Develop and maintain web applications using Ruby on Rails as the primary technology. Collaborate with cross-functional teams to design and implement scalable solutions. Contribute to the architecture and development of microservices, where applicable. Utilize Node.js and React technologies to enhance application features and performance. Participate in code reviews and ensure adherence to best practices and coding standards. Communicate effectively with stakeholders to understand project requirements and deliver solutions accordingly. Qualifications Proven commercial experience in Ruby on Rails development. Experience working with modern web applications and frameworks. Exposure to Node.js and/or React technologies. Understanding of microservices architecture is preferred. Strong problem-solving skills and ability to work collaboratively within a team setting. Very good English level. Benefits Opportunity to participate in a cutting-edge project with a dynamic and innovative team. Professional growth through engagement in technical interviews and project development phases. Remote work (Poland). Exposure to a diverse technology stack including Ruby on Rails, Node.js, React, and microservices. Unique TEAL culture, relationship- and respect-driven community, non-corporate atmosphere. Agile approach and no bureaucracy. Outstanding integration trips to various places in Europe for all employees. Activities to support your well-being and health. Luxmed Gold Extended medical care and Multisport Plus benefit.

🏢 Summary: Remote freelance fullstack engineering role focused on building and improving developer-facing SaaS products and real-time infrastructure tools. The position involves owning features end-to-end, from concept and implementation to monitoring in production, using Ruby on Rails, React, and TypeScript. Engineers are expected to drive product outcomes, improve developer experience, and collaborate proactively in an ambiguity-friendly environment. 🗂️ Requirements: Strong Ruby, Strong Rails, Strong React, Experience with TypeScript, Fullstack development experience, Ability to work across frontend and backend, Comfort working with vague requirements, Ownership of features through production lifecycle, Proactive communication skills, Experience using AI coding assistants, Design and UX awareness 📃 Skills: Ruby, Rails, React, TypeScript, Node, PostgreSQL, JavaScript, AI 🏢 Description: Location: Remote · Collaboration: Freelance, via Monterail Tech Network · Start: ASAP The project Some products you use every day without ever seeing them. This is one of those. Our client is a well-established B2D (business-to-developer) SaaS platform -real-time infrastructure that moves billions of messages a day for developers around the world. Live chat, dashboards, collaborative apps, state synchronization: if it updates in front of your eyes, there's a good chance technology like this is running underneath. The role This is a product-minded engineering role, not ticket execution. The team is deliberately moving away from reactive delivery toward engineers who understand customers and drive outcomes. You'll take features from a loose concept to shipped and monitored in production — dashboards, billing UIs, documentation platforms, developer-facing tools — proposing what should be built, not waiting for a roadmap to tell you. And here's the fun part: the customers are developers. You'll use the product yourself and fix the frustrations you'd want fixed. What we're looking for A fullstack craftsman. You're strong in Ruby on Rails and React and comfortable moving across the stack - from complex dashboards to sleek documentation platforms. A DevEx champion. You have natural empathy for other developers and genuinely care about the developer experience of the tools you build. Comfortable with ambiguity. You thrive when the brief is vague. You identify problems, propose solutions, and ship with minimal hand-holding. An owner. You see features through their entire lifecycle — from the first line of code to the final metric in production. Quality issues that surface after release are still yours. A proactive communicator. You give realistic estimates, meet your commitments, and speak up early if a timeline is at risk. Fluent with AI coding assistants. The team uses them actively for planning, prototyping, and iteration — you should too, while owning the correctness and quality of everything that ships. Design and UX intuition. You notice when a flow feels wrong and you're not afraid to say so. Tech stack React + TypeScript on the frontend, Ruby on Rails on the backend, some Node/TypeScript services, PostgreSQL underneath. Nice to have Experience building developer-first products or working on B2D platforms Experience with products grown through product-led growth (PLG) Background in real-time, messaging, or infrastructure-adjacent products How the collaboration works This is a freelance engagement through the Monterail Tech Network - you work with us on a B2B basis, embedded in the client's team, with Monterail handling the partnership side. Read more about what freelancing with us looks like at Monterail Tech Network . Sound like you? Send us your resume — and if you've built anything for developers before, we'd love to hear about it.

🏢 Summary: Senior Ruby on Rails Developer role focused on building and evolving a cloud-ready product into a scalable, distributed system. The position involves designing architecture, developing core services and APIs, and driving Kubernetes-based deployments with CI/CD automation. You will influence engineering standards and contribute production-ready code in a greenfield development environment. 🗂️ Requirements: 5+ years of software engineering experience, Senior-level Ruby on Rails expertise, Experience building and scaling distributed systems, Knowledge of Kubernetes, Experience with CI/CD pipelines, Experience with Infrastructure as Code, Strong API design skills, Experience with microservices communication, Ability to lead architectural initiatives, Mentoring experience for engineers 📃 Skills: Ruby, Rails, Kubernetes, CI/CD, IaC, API, Microservices, DistributedSystems 🏢 Description: We are looking for an experienced Senior Ruby on Rails Developer to join the team responsible for development of the product, which is evolving into a modern, cloud‑ready solution. In this role, you will have opportunity to influence architectural decisions, contribute production‑ready code, and collaborate closely with cross‑functional teams. Your daily responsibilities: Build and improve core platform services and APIs Design scalable, distributed system architecture Implement and optimize key components in the codebase Set engineering standards for reliability and maintainability Drive deployments using Kubernetes and CI/CD automation Collaborate across teams to align technical and product goals. Requirements: 5+ years of software engineering experience, including senior‑level work Strong proficiency in Ruby on Rails Experience building and scaling distributed systems Solid knowledge of Kubernetes, CI/CD, and IaC Strong skills in API design and microservice communication Ability to lead architectural initiatives and mentor other engineers. What we offer: Attractive salary and benefits package, including Multisport card, insurance, and medical care Hybrid work from the Krakow office International work environment in a product company Training and development opportunities within the organization Joining the greefield project with pure development. Apply now!

🏢 Summary: Senior Full Stack Engineer role focused on designing and delivering scalable, cloud-native applications across backend, frontend, and cloud infrastructure. The position involves building high-performance Java systems, modern React interfaces, and deploying solutions on Azure in a distributed enterprise environment. The engineer contributes to architecture decisions and ensures reliable CI/CD and production operations. 🗂️ Requirements: 7+ years Java experience, Strong enterprise backend development, Experience with ReactJS, Experience with Azure cloud platform, Strong PostgreSQL knowledge, Relational data modeling skills, 2+ years CI/CD experience, Experience with DevOps practices, Ability to work across full stack, Strong debugging skills in distributed systems 📃 Skills: Java, ReactJS, Azure, PostgreSQL, CI/CD, DevOps, Microservices, SQL, Cloud, Git 🏢 Description: Senior Full Stack Engineer (Java, Cloud & React) We are looking for a Senior Full Stack Engineer who can take ownership of designing and delivering scalable, cloud-native applications. The role involves working across backend services, frontend interfaces, and cloud infrastructure in a highly distributed enterprise environment. What you will do Design and build high-performance backend systems using Java 17+ Develop modern, responsive UI applications using ReactJS Build and deploy cloud-native applications on Microsoft Azure Work with PostgreSQL for scalable and efficient data design Collaborate with DevOps teams to ensure smooth CI/CD pipelines and releases Debug and resolve complex production issues across distributed systems Contribute to architecture discussions and technical decision-making What we are looking for Strong hands-on expertise in Java (7+ years) and enterprise backend development Solid experience in ReactJS-based frontend development Experience working with cloud platforms (Azure preferred) Strong understanding of PostgreSQL and relational data modeling Exposure to DevOps practices and CI/CD pipelines (2+ years) Ability to work across the stack and handle production-grade systems Strong problem-solving and debugging skills Nice to have Experience designing microservices-based architectures Exposure to large-scale distributed systems Experience working in enterprise-grade cloud environments Interested? Share your CV to a company who matters about your growth and long term prospects.

🏢 Summary: Senior Software Engineer role focused on developing and scaling a robust platform using Ruby on Rails, with responsibility for building secure services and APIs. The position involves implementing new features, improving system performance, and supporting integrations with external partners. This hybrid role in Warsaw includes technical ownership of developed services and participation in agile processes. 🗂️ Requirements: Minimum 5 years of professional Software Engineering experience, Strong proficiency in Ruby on Rails, Experience with React and component-based frameworks, Working knowledge of JavaScript or TypeScript, Experience developing and managing APIs, Ability to work in a hybrid (office/remote) model, Advanced written and spoken English 📃 Skills: Ruby, Rails, React, JavaScript, TypeScript, GraphQL, APIs, Agile 🏢 Description: Our Client, an American software company is opening a new branch in Warsaw and we are looking for a Senior Software Engineer with Ruby to join a growing team. About the Position This role focuses on enhancing and maintaining a robust platform, supporting new project initiatives, and delivering scalable solutions that improve the user experience for both industry professionals and individual clients. The ideal candidate is proactive, collaborative, and committed to delivering high-quality, scalable software. This is a hybrid role based in Warsaw, Poland. Key Responsibilities Design and implement new functionalities for a cutting-edge platform Develop and manage APIs to enable smooth integration with financial and sales partners Build secure and scalable services designed for sustained performance Support agile development practices and help ensure consistent, impactful sprint results Mentor team members and contribute to a positive engineering culture through knowledge-sharing Maintain and take responsibility for services you develop, including participating in the on-call rotation Requirements Minimum 5 years of professional experience as a Software Engineer Strong proficiency with Ruby on Rails Excellent communication skills and experience working in cross-functional teams Familiarity with React and component-based front-end frameworks Working knowledge of JavaScript and/or TypeScript Ability to perform in a hybrid (office/remote) work environment Advanced written and spoken English (please provide your CV in English) Nice to have Experience with GraphQL

🏢 Summary: Full-Stack Developer (Ruby on Rails) role within an R&D team building advanced life science research platforms. The position involves designing and delivering scalable, secure web solutions across frontend and backend, contributing to architecture and product direction. The engineer will work in an agile environment to enhance a multi-tenant SaaS platform used globally by researchers. 🗂️ Requirements: Minimum 3 years of professional web development experience, Strong hands-on experience with Ruby on Rails, Solid backend and frontend development knowledge, Experience with HTML, CSS, and JavaScript, Experience building and maintaining APIs, Experience with AWS and CI/CD pipelines, Proficiency with Git, Experience with AI-assisted development tools, Ability to develop scalable and secure applications 📃 Skills: Ruby, Rails, HTML, CSS, JavaScript, Hotwire, React, AWS, CI/CD, Git, Docker, MySQL, Elasticsearch, APIs 🏢 Description: For one of our clients, we are currently seeking an experienced Full‑Stack Developer (Ruby on Rails) to join an R&D team building advanced platforms for life science research. This role is ideal for an engineer who values clean architecture, high‑quality code, and modern web development practices. You will become part of an agile, highly motivated engineering team responsible for building and evolving a platform used daily by researchers and laboratories worldwide. As an experienced engineer, you will play a meaningful role in shaping the technical direction of the product and driving future platform improvements. Working closely with product leaders and management, you will ensure that our solutions continue to meet the needs of a growing scientific community. What You Will Do Design, implement, and ship new features as well as future releases of the platform across frontend and backend layers. Build, improve, and maintain robust platform APIs with a strong focus on scalability, reliability, and performance. Write clear, maintainable, and well‑tested code, following iterative and test‑driven development principles. Collaborate closely with product and management teams to transform business requirements into effective technical solutions. Help develop a highly scalable service deployed in multi‑tenant SaaS, single‑tenant SaaS, and on‑premise environments. Apply secure development practices and contribute to system scalability and performance optimization. Actively use AI‑assisted development tools to speed up coding, reviews, and testing workflows. Contribute positively to team collaboration, sharing ownership and fostering a supportive and enjoyable work culture. Experience & Technical Requirements Required: Minimum of 3 years of professional experience in web development, with solid knowledge of both backend and frontend development. Required: Strong, hands‑on experience with Ruby on Rails . Experience with several of the following technologies: HTML, CSS, JavaScript, Hotwire, React, AWS, CI/CD pipelines, Git . Experience with Docker is considered an advantage. Experience with MySQL is a plus. Experience with Elasticsearch is a plus. Hands‑on use of AI‑powered tools to accelerate development (e.g. AI‑assisted coding, automated code reviews, or testing). Experience integrating AI workflows into the software development lifecycle is considered a nice‑to‑have. Who You Are A collaborative team member who raises the technical bar and encourages excellence in others. Comfortable explaining ideas, designs, and decisions to both technical and non‑technical stakeholders. Able to thrive in a fast‑paced, agile environment where results are delivered in short cycles. Opinionated about technology choices and how to apply them effectively to deliver real value to users and the business. A pragmatic yet passionate polyglot programmer with a strong software engineering foundation. Open to experimenting with and adopting AI tools as part of everyday development work. Willing to work from the office at least two days per week, with flexibility to work remotely when needed. A background or degree in Life Sciences is a significant advantage. Hays Poland sp. z o.o. jest agencją zatrudnienia zarejestrowaną w rejestrze prowadzonym przez Marszałka Województwa Mazowieckiego pod numerem 361.